When a user tries to access a server that requires an authentication of the user, one way of authentication is to send the user a PIN code by another means of communication. Such a means of communication is usually a mobile phone or of the like. The PIN code is sent to the user usually as an SMS on his or her registered phone. The user then types in the PIN code and gets access to the information on the server.
This method is widely used, but has its limitations. Under certain circumstances it can be a problem reaching the user with an SMS. An example is sending a SMS from a GSM network to a GSM phone user roaming in a CDMA network.
This is a problem e.g. for Europeans trying to receive a PIN code from a European site whilst being in America.
From U.S. Pat. Nos. 6,748,367 B1 and 6,205,437 B1 it is known a solution for distributing a PIN code to a cell phone either using SMS, e-mail, a phone call or similar.
The problem with these solutions is that they do not solve the problem mentioned above. Sending the PIN code with an e-mail reduces the security of the distribution since it is not sent through a different means of communication. Further sending it via an phone call is unnecessarily expensive since you need to have a person phoning the end user in a foreign country. Additionally, incorporating a person to distribute the PIN code reduces the security level of the authentication.